What Went Wrong: Torture and the Office of Legal Counsel in the Bush Administration: Hearing Before the Subcomm. on Administrative Oversight and the Courts of the S. Comm. on the Judiciary, 111th Cong., May 13, 2009 (Statement of David Luban, Prof. of Law, Geo. U. L. Center)
The mission of the Office of Legal Counsel is to give the President advice to guide him in fulfilling an awesome constitutional obligation: to take care that the laws are faithfully executed. Faithful execution means interpreting the law without stretching it and without looking for loopholes. OLC's job is not to rubber-stamp administration policies, and it is not to provide legal cover for illegal actions.
Unfortunately, the interrogation memos fall far short of professional standards of candid advice and independent judgment. They involve a selective and in places deeply eccentric reading of the law. The memos cherry-pick sources of law that back their conclusions, and leave out sources of law that do not. They read as if they were reverse engineered to reach a pre-determined outcome: approval of waterboarding and the other CIA techniques.